I have the Truma as well as the Dometic (the Dometic was a gift) I never have an empty tank to test them on, so I let my propane run the fridge after the Pismo Rally in hopes that I can get a reading with the Truma and the Dometic...
I'll post back here with a review of the Truma unit after I test it. Thanks Jeff for the heads up on the "C" grade.
WoodGlue